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Lubricants 2018, 6(2), 40; https://doi.org/10.3390/lubricants6020040

Dynamical Simulations of a Flexible Rotor in Cylindrical Uncavitated and Cavitated Lubricated Journal Bearings

1
Department of Industrial Engineering, University of Salerno, 84084 Salerno, Italy
2
Department of Mechanical Engineering, Chemical and Industrial Design, Universidad Politécnica de Madrid (UPM), 28012 Madrid, Spain
3
Mechanical Engineering Faculty in Slavonski Brod, J. J. Strossmayer University of Osijek, HR-35000 Slavonski Brod, Croatia
*
Author to whom correspondence should be addressed.
Received: 5 February 2018 / Revised: 16 April 2018 / Accepted: 20 April 2018 / Published: 25 April 2018
(This article belongs to the Special Issue Tribology of Machine Elements--Smart Lubricants)

Abstract

Due to requirements of their operating conditions, such as high speed, high flexibility and high efficiency, rotating machines are designed to obtain larger operating ranges. These operating conditions can increase the risk of fluid-induced instability. In fact, the presence of non-linear fluid forces when the threshold speed is overcome by the rotational speed, can generate rotor lateral self-excited vibrations known as “oil whirl” or “oil whip”. These instabilities derive from the interaction between the rotor and the sliding bearing and they are typically sub-synchronous and they contribute to eventual rubbing between rotor and stator with consequent damage to the rotating machines. For these reasons, the aim of this paper is to numerically investigate the differences in the dynamic behaviour of a flexible rotor supported by cylindrical lubricated journal bearings. The study considers two different cases, uncavitated and cavitated lubricated films, in order to develop an original Matlab-Simulink algorithm for the numerical solution of the differential non-linear equations of motion of the unbalanced flexible rotor supported on hydrodynamic journal bearings. The bearings were modelled as uncavitated and cavitated (π-Film) short bearings derived from classical Reynolds’ theory. Dynamic simulation allowed prediction of the shape and size of the orbit performed by the system and evaluation of the vibrating phenomena exerted by the rotor during the motion. The results show that cavitation completely modifies the behaviour of the system in every aspect. The analysis of the diagrams obtained showed that the proposed algorithm provides consistent results and represents a valuable instrument for dynamic analysis of rotating systems. View Full-Text
Keywords: rotor dynamics; journal bearing; cavitation; Matlab-Simulink algorithm rotor dynamics; journal bearing; cavitation; Matlab-Simulink algorithm
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Ruggiero, A.; D’Amato, R.; Magliano, E.; Kozak, D. Dynamical Simulations of a Flexible Rotor in Cylindrical Uncavitated and Cavitated Lubricated Journal Bearings. Lubricants 2018, 6, 40.

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